    <ul class="easyui-tree">
    <li>
    <span>Folder</span>
    <ul>
    <li>
    <span>Sub Folder 1</span>
    <ul>
    <li><span>File 11</span></li>
    <li><span>File 12</span></li>
    <li><span>File 13</span></li>
    </ul>
    </li>
    <li><span>File 2</span></li>
    <li><span>File 3</span></li>
    </ul>
    </li>
    <li><span>File21</span></li>
    </ul>